Hi all!

I am a Windows power user and I always had, even with different PC and
RAM quantity, a problem recurring atleast one time a day: when I have
opened more than 20-30 programs, the opening of new windows/programs
doesn't have effect or gives progressively strange effects (i.e.
windows without menu and buttons) till it doesn't do anything anymore.

In this precise moment it's happening on my XP. 
My strong suspect is that this has always been an internal software
limitation (connected to the limited size of resource heaps) of
Windows NT/2K/XP, as when in Windows 3.x/9x/ME one got the
"insufficient memory" error.

My Task Manager is showing the following data and I can't open even
little applications without closing some application before:

Totals:
 Handles: 23194
 Threads: 1249
 Processes: 74

Physical Memory (K):
 Total: 752016
 Available: 154048
 System Cache: 230176

Commit Charge (K):
 Total: 1367024
 Limit: 1871520
 Peak: 1448860

Kernel Memory (K):
 Total: 182012
 Paged: 158696
 Nonpaged: 23316

Anyway I don't think there's a strict relation of this problem with
the total physical memory or the total physical+virtual memory. I
think more that it's an intrinsic Windows limitation. I think that
it's a matter of system resources/resource heaps instead of memory, as
this article describes well: http://aumha.org/win4/a/resource.php
(System Resources FAQ).

In the case I try to launch a graphic Win16 application I get the
explicit error: "The Win 16 Subsystem has insufficient resources to
continue running. Click on OK, close your applications, and restart
your machine." Fortunately it's normally sufficient to close some
application, without restarting, to come back to use the program.
Setting this application to "Run in separate memory space" or setting
it in Compatibility Mode 9x doesn't solve.

***I'ld like to find a document with the "ultimate" explanation of how
is this limitation in Windows XP (NOT an old document regarding
3.x/9x/ME nor NT) and to find the way to increase the number of
application I can open simultaneously or, if this is not possible, how
and how much in the future this limitation will be enhanced by
Microsoft in future versions of Windows.***

I found this software that could help for win 16 programs but it's too
old: http://www.qualitas.com/tech/max/goahead.htm.
and I found this opinion on the net: "Ron M. replies:
RAM Defrag programs are totally useless and cannot perform any
beneficial function for any computer. Period.
All RAM addresses are equally accessible and there is zero difference
in the time required to access addresses at the opposite ends of the
RAM address range as compared to adjacent addresses. Both are
virtually instantaneous.
Also "system resources" as the term was used in Windows 95/98/Me are
totally irrelevant in Windows XP because XP uses 32 bit resource heaps
exclusively."

Thanks,
Marco Venturi

You may be able to overcome this by buying more RAM. However why do
you need to run 20-30 programs? Is it programs or processes?? You
should not need to run 20-30 programs

I passed from 256MB to 768MB of real RAM and the open programs'limit
seems the same.
Furthermore, I expanded the virtual memory to 4GB and the limit seems
the same of just a little higher. In this case, when I encounter the
limit the occupied VM is about 1,1GB, so there are 2,9GB of free VM.
Furthermore, the Task Manager shows that I've still abundant free RAM
and VM when I encounter the limit.

It's not the RAM quantity, as it was not the RAM qty in Windows 9x. In
Windows 9x you can easily verificate that it's not the RAM qty using
the "resource meter". You will always have the same resource quantity,
no matter of how much RAM you have. And when you reach the 0 resource
you can't open any programs anymore.